Start with a 36-grit orbital sandpaper disc.
There are two general ways to sand a wood floor in preparation for refinishing. One is to use a drum sander, in which the sandpaper is a large belt that runs continuously against the floor. The other is to use an orbital sander, in which the sandpaper is a disk that turns in circles against the floor's surface. Orbital sanding is the gentler process, which is the way to go if the floor is a little older and has perhaps already been sanded a time or two.
Instructions
1. Pry off the floor trim with a hammer and pry bar. Go over the, floor section by section with your hammer and nail set, sinking any raised nail heads that are sticking up. Thoroughly vacuum the floor.
2. Load your orbital floor sander with the heaviest abrasion of sandpaper (the lowest number) -- in this case, 36-grit. Typically, you will lay the circular sandpaper on the floor and set the orbital pad of the sander on top of it, with the weight of the sander holding the paper to the floor, though some styles vary. Consult the instructions that came with your sander to be sure.
3. Run the orbital sander with the direction of the floorboards, starting along one wall and working your way across the floor. Do the whole floor, scraping off any surface grime and gloss. Never let the sander stand in one place while it's on.
4. Vacuum up the dust.
5. Put the next highest abrasion level of paper in the sander (50-grit) and repeat the sanding process. It will take off the last of the top layer of material and start to smooth out the rough surface left by the initial sanding. Vacuum again.
6. Repeat the process twice more with the next two successively finer abrasion levels of paper (80-grit and 120-grit), to get the surface completely smooth. Vacuum between each sanding.
